DSOs under a fullmoon - red filter to rescue

[nytecam]

I'm currently running my 12" SCT at an absurd f/2.3 'speed' [almost Hyperstar-like] by shifting the SX L-Mx2 sensor as far back as practical from the Mead f/3.3 focal reducer. It reduces the effective 'scope focal length from its native f/10 @ 3000mm fl to f/2.3 @ 700mm fl to cover a much larger 32' x 25' fov.

But it causes problems - some coma distortion as the edge of the field and vignetting as darker corners.  Perhaps more importantly the sensor due to its extreme 'speed', skyfogs in <40s under my white/red zone London skies eg complete 'whiteout' of the image.  The current full moon make it even worse ! It's partially resolved by using a 1-1/4" screw-in red filter in the camera nosepiece which suppresses all wavelengths except red and near-IR so that exposures to 1min are possible. There's a bonus : enhanced H-alpha in emission nebula.  The vignetting is minimised by applying a suitable 'flat' to the images.

Here's a few examples:  M57 + central star in 30s and NGC 383 galaxy group in Pisces @ 210MLY in 2m [4x30s summed] in the camera's 2x2 binned mode under SX s/w option and rescaled larger.  More to follow

[orion25]

Wow! That's impressive. Great work! Looking forward to seeing more 

[nytecam]

Thanks Orion25 - here's M33 Pinwheel binned 2x2 in 150s [5x30s summed]; Bubble NGC 7635 raw/no flat/dark/ centre boost; M27 Dumbbell in 120s [4x30s summed] plus older SX L-C image and RGB channel split showing the mono image mimics the red channel. Taken same night and set-up under full moon - LP+moonlight takes its toll on images